1. Field of the Invention
The present invention relates to a thin film synthesizing process and, more specifically, to a barium titanate film synthesizing process to synthesize barium titanate film with uniformly dispersed particles at a low temperature close to room temperature within a short electrolytic duration.
2. Description of the Related Art
Barium titanium is an important functional material for the advantages of superior dielectric, ferroelectric and piezoelectric properties. Following fast development of technology, products are made thinner, lighter, shorter, and smaller. Barium titanate films have many applications. For example, in designing ULSI DRAM, SiO2/Si3N4 is used as capacitance material. However, increasing capacitance area requires a three-dimensional stacking and geographical grooving design. Using barium titanate films to substitute for SiO2/Si3N4 could maintain plane geometric structure under a reduced capacitance size.
Various methods have been used to synthesize barium titanate film, including sputtering, evaporation, chemical vapor deposition, laser coating, sol-gel, hydrothermal and electrochemical processes, etc. Electrochemical process is superior to the other methods for the advantages of simple set-up of instruments, low processing temperature, high deposition rate, and easy formation of crystallized film. Electrochemical deposition of barium titanate film can be achieved by cathodic reduction or anodic oxidation. Cathodic reduction often results in amorphous structure which must be further heat-treated to yield crystalline structure. Moreover, the film surface is generally porous. On the other hand, electrochemically anodic oxidation can also be used to synthesize barium titanate films on substrates in an alkaline solution of Ba(OH)2 or Ba(CH3COO)2. Uniformly dispersed spherical particles are seen in barium titanate films synthesized by this method. The quality of barium titanate films synthesized by electrochemically anodic oxidation is superior to that obtained by cathodic reduction. Electrochemically anodic oxidation normally yields crystalline phase, hence no further heat treatment is necessary. However, titanium substrates must be used in electrochemically anodic oxidation. Manufacturers are developing economical processes with simple set-up of instruments and a considerably fast growth rate.